Greens concerned by Xenophon deal

Independent Senator Nick Xenophon has put the coalition in the box seat to take control of the Senate by not preferencing the Greens at next month's election, Greens Senator Sarah Hanson-Young says.

Senator Xenophon will advise his supporters to put the Liberal or Labor parties ahead of the Greens at the September 7 poll, making it harder for Senator Hanson-Young to be returned.

She may need preferences to retain her seat and Senator Xenophon's move could now help send a third Liberal from South Australia to Canberra.

Senator Hanson-Young said Senator Xenophon's decision was "his choice" but urged progressive voters to be mindful of the potential consequences.

"He has opted to preference (Opposition Leader) Tony Abbott to win the last Senate seat here in South Australia, which puts Tony Abbott in the box seat to take effective control of the Senate," she said on Friday.

Senator Hanson-Young said she believed many progressive voters would be disappointed by Senator Xenophon's decision.

Senator Xenophon said an overwhelming reaction against the Greens from his supporters had convinced him to preference the major parties first on his SA Senate ticket.